Integrate circuits may integrate different types of circuits on a single chip to increase integration level. For example, an integrated circuit chip may include integrated analog circuit, digital circuit, memory, and/or input output (IO) circuit, etc.
Different types of integrated circuits may use different supply voltages. Thus, an integrated circuit chip may need different supply voltages for different parts of the chip.
For example, it may be preferred to use low supply voltage for internal digital cores of integrated circuits. Short channel length can be used to reduce die size and/or to increase the speed. Associated with the use of short channel length is the thin gate oxide thickness, which requires low power supply voltages. Thus, a digital circuit on the integrated circuit may need a voltage lower than an analog circuit implemented on the same integrated circuit.
Further, the power consumption of the digital circuits implemented in complementary metal oxide semiconductor (CMOS) logic is approximately proportional to the square of its supply voltages. Low supply voltage can be used to reduce power consumption of the integrated digital circuits.
Input output (IO) circuits and analog circuits may run at a supply voltage different from that of the integrated digital core of an integrated circuit chip. Input output (IO) circuits and analog circuits may be required to interface directly with signals coming to or going out of the integrated circuit chip. The signals off the integrated circuit chip may have different common-mode voltages, large voltage swing, etc. Typically, input output (IO) circuits and analog circuits run at higher supply voltages than integrated digital circuit core of an integrated circuit.
To meet the requirement of multiple supplies for an integrated circuit, off-chip supply regulators are typically used to provide different power voltages for the integrated circuit. Philips TDA10023 (Philips Semiconductor, TDA10023 www.philips.com) is such an example. Another example is Zarlink ZL10210, the Datasheet released 2005.